Method and apparatus of multicast service flow processing for headend cable modem

ABSTRACT

A method and apparatus of processing a multicast service flow for a headend cable modem is provided. 
     The method of processing the multicast service flow includes: classifying an inputted multicast packet by a session; composing an internal header including multicast service flow information allocated to the classified session; and outputting an internal multicast packet including the internal header.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from Korean Patent Application No.10-2007-0127381, filed on Dec. 10, 2007, in the Korean IntellectualProperty Office, the entire disclosure of which is incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to service flow processing in a network,for example, a Hybrid Fiber Coax (HFC) network, and more particularly,to a method and apparatus of processing a multicast service flow for aheadend cable modem in an HFC network using a channel bonding scheme.

This work was supported by the IT R&D program of MIC/IITA[2006-S-019-02, The Development of Digital Cable Transmission andReceive System for 1 Gbps Downstream].

2. Description of Related Art

A Hybrid Fiber Coax (HFC) network is a network including an opticalfiber and a coaxial cable, and is a broadband transmission network totransmit a data signal (for the Internet, a cable television (TV), crimeprevention, disaster prevention, remote inspection of a meter, andautomatic control) using the optical fiber to a broadcasting station andan Optical Network Unit (ONU), and using the coaxial cable from the ONUto subscribers.

Internet Protocol (IP) multicast denotes a point-to-multipointtransmission scheme to transmit a packet to a specific service group,and includes an Any Source Multicast (ASM) scheme of classifying asession by only a receiving group address without identifying atransmitter, and a Source Specific Multicast (SSM) scheme of classifyingthe session by the transmitter even in the case of the same receivinggroup address, based on a configuration form of a multicast session.

FIG. 1 illustrates a multicast concept in Data Over Cable ServiceInterface Specifications (DOCSIS).

Referring to FIG. 1, all multicasts of an ASM scheme and an SSM schemeneed to be supported in DOCSIS 3.0 being a standard of a cable networksupporting channel bonding.

A headend Cable Modem Termination System (CMTS) 101 attaches aDownstream Service Identification (DSID) to all coming multicast serviceflows. The CMTS 101 transmits, to cable modems (CMs) 104 and 105,multicast service flows 102 and 103 to which the DSID is attached.

The CMTS 101 following DOCSIS 3.0 assigns the unique DSID to allmulticast traffic composing the multicast session, and transmits themulticast service flow 102 to the CM 104, and the CM 104 performsfiltering based on the DSID without identifying a group address withrespect to the multicast session.

However, according to pre-DOCSIS 3.0, the CM 105 controls whether amulticast packet is transmitted, using a snooping operation of aprotocol unit to join in a multicast group and leave from the multicastgroup.

In DOCSIS 3.0 using a channel bonding scheme, the CMTS 101 needs toclassify a service flow so that the CM receiving a packet with respectto a single multicast session may not overlappingly receive the packetof the same multicast session.

A single multicast packet coming from a network service interface to theCMTS 101 may generate at least one multicast service flow based on aphysical form (in the cable network) of a receiving group at which themulticast session intends to arrive.

Accordingly, a multicast packet processor (not shown) located in a MediaAccess Control (MAC) layer of the CMTS 101 needs to identify themulticast session corresponding to the multicast packet, identify themulticast service flow allocated to the identified session, compose aninternal information header included in the inputted packet based onrelated information of the service flow, copy a plurality of multicastdata packets, and transmit the plurality of multicast data packets tothe CM.

SUMMARY OF THE INVENTION

An aspect of the present invention provides a method and apparatus forclassifying a downstream multicast packet inputted from a networkservice interface to a Cable Modem Termination System (CMTS) by amulticast session, classifying service flows corresponding to theclassified multicast session, and composing information about acorresponding service flow as an internal header.

Another aspect of the present invention also provides a method andapparatus for copying a multicast packet the same number of times as anumber of service flows when at least one multicast service flowallocated to the classified session exists, composing a downstreamservice identifier related to a corresponding service flow and relatedservice flow information as an internal header in the copied packet.

Another aspect of the present invention also provides a data structurefor classifying a multicast packet by a multicast session, classifyingservice flows corresponding to the classified multicast session, andcomposing information about a corresponding service flow as an internalheader.

According to an aspect of the present invention, there is provided amethod of processing a multicast service flow in a CMTS, the methodincluding: classifying an inputted multicast packet by a session;composing an internal header including multicast service flowinformation allocated to the classified session; and outputting aninternal multicast packet including the internal header.

According to another aspect of the present invention, there is provideda method of processing a multicast service flow in a CMTS, the methodincluding: verifying whether an inputted downstream data packetcorresponds to a multicast packet, using a destination address of theinputted downstream data packet; searching to verify whether multicastsession information exists when the inputted downstream data packetcorresponds to the multicast packet; composing an internal headerincluding multicast service flow information allocated to a session whenthe multicast session information about the inputted downstream datapacket exists; and outputting the multicast packet including thecomposed internal header.

According to still another aspect of the present invention, there isprovided an apparatus for processing a multicast service flow in a CMTS,the apparatus including: a multicast packet processor to classify aninputted multicast packet by a session, to add an internal header to themulticast packet, the internal header including multicast service flowinformation allocated to the classified session, and to output themulticast packet; and a header processor to compose a multicast MACpacket based on the internal header, to perform downstream scheduling ofthe multicast packet using the same scheme as a general service flow,and to transmit the MAC packet to a downstream physical layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects of the present invention will becomeapparent and more readily appreciated from the following detaileddescription of certain exemplary embodiments of the invention, taken inconjunction with the accompanying drawings of which:

FIG. 1 illustrates a multicast concept in Data Over Cable ServiceInterface Specifications (DOCSIS);

FIG. 2 is a block diagram illustrating a configuration of an apparatusfor processing a multicast service flow according to an exemplaryembodiment of the present invention;

FIGS. 3A through 3C illustrate input/output packet configurationsaccording to an exemplary embodiment of the present invention;

FIG. 4 is a block diagram illustrating a configuration of an apparatusfor processing a multicast service flow according to another exemplaryembodiment of the present invention;

FIG. 5 is a flowchart illustrating a method of processing a multicastservice flow according to an exemplary embodiment of the presentinvention; and

FIG. 6 is a flowchart illustrating an operation of a multicastcontroller according to an exemplary embodiment of the presentinvention.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Reference will now be made in detail to exemplary embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings, wherein like reference numerals refer to the like elementsthroughout. The exemplary embodiments are described below in order toexplain the present invention by referring to the figures.

When detailed descriptions related to a well-known related function orconfiguration are determined to make the spirits of the presentinvention ambiguous, the detailed descriptions will be omitted herein.Also, terms used throughout the present specification are used toappropriately describe exemplary embodiments of the present invention,and thus may be different depending upon a user and an operator'sintention, or practices of application fields of the present invention.Therefore, the terms must be defined based on descriptions made throughthe present invention.

FIG. 2 is a block diagram illustrating a configuration of an apparatus200 for processing a multicast service flow according to an exemplaryembodiment of the present invention.

Referring to FIG. 2, the apparatus 200 for processing the multicastservice flow includes a multicast packet processor 201 and a headerprocessor (a Data Over Cable Service Interface Specifications MediaAccess Control (DOCSIS MAC) header processor) 204.

The multicast packet processor 201 classifies an inputted multicastpacket by a session, adds an internal header to the multicast packet,the internal header including multicast service flow informationallocated to the classified session, and outputs the multicast packet.

An input packet configuration 301 of the multicast packet processor 201is illustrated in FIG. 3A. An output packet configuration 302 of themulticast packet processor 201 is illustrated in FIG. 3B.

The multicast packet processor 201 acquires service flow informationrelated to the inputted multicast packet, copies the multicast packetnecessary multiple times, adds the internal header to each multicastpacket, and outputs the multicast packet.

The multicast packet processor 201 searches for an address of a serviceflow information table from a multicast lookup table including serviceflow address information corresponding to the classified multicastsession, and extracts internal header information including downstreamservice identifier information from the service flow information tableand composes the internal header.

The header processor 204 composes a multicast MAC packet based on theinternal header, performs downstream scheduling of the multicast packetusing the same scheme as a general service flow, and transmits the MACpacket to a downstream physical layer.

The header processor 204 generates a DOCSIS MAC packet in an outputpacket configuration 303 of FIG. 3C regardless of a service flow typebased on internal header information of a predetermined form, andtransmits the DOCSIS MAC packet to a cable modem (CM) using a downstreamphysical layer interface. Since the multicast service flow outputted bythe multicast packet processor 201 used for an exemplary embodiment ofthe present invention is reflected on downstream channel transmissionscheduling through the same packet transmission process as a generalunicast service flow and a broadcast service flow without passingthrough a separate header processing process, independent modularitywith respect to a transmission processing process of the multicastservice flow may be secured.

The output packet configuration 303 of the header processor 204 isillustrated in FIG. 3C.

The apparatus 200 for processing the multicast service flow may includea multicast session lookup table 202 to be composed to search for theaddress of the service flow information table using a receiving groupaddress of the inputted multicast packet and a transmission address as asearch character string.

According to another exemplary embodiment of the present invention, themulticast session lookup table 202 may be included the multicast packetprocessor 201.

The apparatus 200 for processing the multicast service flow may includea multicast service flow information table 203 to include at least oneof information concerning whether a channel bonding service of themulticast packet is provided, transmission priority information, adownstream channel list, a downstream service flow identifier, and asubsequent link address of a service flow connected with a linked list.

According to another exemplary embodiment of the present invention, themulticast service flow information table 203 may be included themulticast packet processor 201.

The multicast packet processor 201 refers to the multicast sessionlookup table 202 and the multicast service flow information table 203 inorder to acquire the service flow information related to the inputtedmulticast packet.

FIG. 4 is a block diagram illustrating a configuration of an apparatus400 for processing a multicast service flow according to anotherexemplary embodiment of the present invention.

Referring to FIG. 4, the apparatus 400 for processing the multicastservice flow includes a multicast packet processor 401, a multicastsession lookup table 402, a multicast service flow information table403, a multicast controller (a DOCSIS multicast controller) 406, and anInternet Group Management Protocol (IGMP) snooping processor 407.

The multicast packet processor 401 performs the same function as themulticast packet processor 201 of FIG. 2.

According to an exemplary embodiment of the present invention, themulticast session lookup table 402 may be composed by a cyclic accessmemory (CAM) search scheme or a ternary content addressable memory(TCAM) search scheme.

According to an exemplary embodiment of the present invention, a datastructure of the multicast session lookup table 402 is formed to searchfor an address of a service flow information table with respect to acorresponding multicast session using an Ethernet MAC address denoting areceiving group address of an inputted multicast packet (hereinafter,referred to as a GMAC address), and an Ethernet MAC address denoting atransmission address (hereinafter, referred to as an SMAC address) as asearch character string.

The multicast service flow information table 403 may include a staticrandom access memory (SRAM), and include a linked list 404 of a serviceflow and an information storage table 405.

Accordingly, service flows allocated to a session by setting an addressfield acquired from session information of the multicast session lookuptable 402 as a start entry are connected with the linked list 404.

A single multicast session may generate at least one service flow, andinformation about each service flow entry may include fields such as theinformation storage table 405.

Referring to the information storage table 405, the information abouteach service flow entry includes at least one of a packet (Pkt) typefield denoting a type of a DOCSIS MAC header of the multicast packet tobe transmitted, header configuration information, and whether a channelbonding service is provided, a Downstream Service Identification (DSID)field, a transmission priority field to be applied to downstream packettransmission scheduling, a Downstream Channel (DC) list field to beavailable when supporting a channel bonding function, a DownstreamService Flow Identification (DS SFID) field, and a next link fielddenoting an address of a subsequent connected link.

The information included in each field of the information storage table405 is referred for scheduling and a header processing process of adownstream packet processor in which header processing with respect to aDOCSIS MAC packet and downstream transmission scheduling are performed.

As illustrated in FIG. 3B, the information included in each field of theinformation storage table 405 is applied to an internal header field tobe added to a front portion of the inputted multicast packet.

The multicast controller 406 generates the multicast service flow withrespect to the multicast session collected by the IGMP snoopingprocessor 407 for an upstream packet or operator specific information,and composes multicast session information.

A control function performed by the multicast controller 406 is aflexible control function to be composed by a hardware or softwarefunction, and includes a management function to generate and delete adownstream multicast session and the service flow.

Hereinafter, referring to the accompanying drawings, specific operationsof the multicast packet processors 201 and 401 are described.

FIG. 5 is a flowchart illustrating a method of processing a multicastservice flow according to an exemplary embodiment of the presentinvention.

Referring to FIG. 5, the method of processing the multicast service flowincludes verifying whether an inputted downstream data packetcorresponds to a multicast packet, using a destination address of theinputted downstream data packet in operations 501 and 502, searching toverify whether multicast session information exists when the inputteddownstream data packet corresponds to the multicast packet in operations503 and 504, composing an internal header including multicast serviceflow information allocated to a session when the multicast sessioninformation about the inputted downstream data packet exists inoperations 505 and 506, and outputting the multicast packet includingthe composed internal header in operation 507.

In operations 501 and 502, when a data packet is inputted, the multicastpacket processors 201 and 401 determine whether a start addresscorresponds to a multicast group address (ex: 01:00:5e start) using anEthernet MAC destination address.

In operation 503, when the start address of the Ethernet MAC destinationaddress corresponds to the multicast group address, the multicast packetprocessors 201 and 401 compose a multicast session search characterstring using a GMAC address and an SMAC address.

In operation 504, the multicast packet processors 201 and 401 search forthe multicast session lookup tables 202 and 402 and determine whethercorresponding session information exists.

In operation 505, when the corresponding session information exists inthe multicast session lookup tables 202 and 402, the multicast packetprocessors 201 and 401 acquire the start address of the multicastservice flow information.

In operation 506, the multicast packet processors 201 and 401 search forservice flow information using the start address of the acquired serviceflow information, and compose the internal header in a front portion ofthe inputted multicast packet by the retrieved information.

In operation 507, the multicast packet processors 201 and 401 output aninternal multicast packet including the composed internal header.

According to an exemplary embodiment of the present invention, at leastone service flow with respect to a single session may exist.

Accordingly, the multicast packet processors 201 and 401 read subsequentlink information of the retrieved service flow information and determinewhether subsequent linked service flow information exists in operation508, acquire corresponding information when the linked service flowexists, in operation 509, and repeat operations 506 and 507.

The multicast packet processors 201 and 401 finally repeat operations506 and 507 until the subsequent link information of the retrievedservice flow information is null in operation 508.

In operation 502, the multicast packet processors 201 and 401 directlyoutput general packets excluding the multicast packet to a downstreampacket processor.

In operation 510, the multicast packet processors 201 and 401 deal withpackets which include a multicast Ethernet MAC address and in which amulticast session is not retrieved in the multicast session lookup tablein operation 504, as the service flow for broadcast.

In operation 510, the multicast packet processors 201 and 401 composethe internal header including information denoting a broadcast serviceflow. In operation 511, the multicast packet processors 201 and 401output the internal multicast packet including the internal header. Thisis for transmitting the corresponding multicast packet using adownstream channel by which the service flow for broadcast istransmitted since searching for a downstream channel group with respectto the session to transmit the corresponding multicast service flowfails.

FIG. 6 is a flowchart illustrating an operation of the multicastcontroller 406 according to an exemplary embodiment of the presentinvention.

Referring to FIG. 6, a control function of the multicast controller 406includes receiving a multicast membership request message and generatingsession information in operations 601 through 604, determining whetherthe generated session information exists in a lookup table when themulticast membership request message corresponds to a message ofrequesting group joining in operations 605 and 606, searching to verifywhether service flow information corresponding to the sessioninformation exists when the session information exists in the lookuptable in operations 608, and generating and storing the service flowinformation when the service flow information corresponding to thesession information does not exist in operations 609 and 610.

In operation 601, the multicast controller 406 receives a message torequest multicast group joining or leaving (the multicast membershiprequest message) using the IGMP snooping processor 407 in an upstreamdata packet processor (not shown), a presetting function of an operator,and the like.

In operation 602, the multicast controller 406 determines whether thereceived multicast membership request message corresponds to a SourceSpecific Multicast (SSM) scheme of identifying a transmission areaaddress.

In operation 603, when the received multicast membership request messagecorresponds to the SSM scheme, the multicast controller 406 adds a GMACaddress and an SMAC address and generates the session information.

In operation 604, when the received multicast membership request messageis different from the SSM scheme, the multicast controller 406 processesmasking of the SMAC address on the GMAC address and generates thesession information.

In operation 605, the multicast controller 406 determines whether amembership request performed by the received multicast membershiprequest message corresponds to a report message of requesting groupjoining.

In operation 606, when the membership request corresponds to the reportmessage, the multicast controller 406 searches to verify whether acorresponding session exists in the multicast session lookup tables 202and 402.

In operation 607, when the corresponding session does not exist in themulticast session lookup tables 202 and 402, the multicast controller406 generates multicast session information and records the multicastsession information in the multicast session lookup tables 202 and 402.

In operation 608, the multicast controller 406 searches to verifywhether the service flow information about the corresponding multicastsession information exists in the multicast service flow informationtables 203 and 403.

The service flow information about the multicast session informationdenotes a service flow to reach a CM having transmitted a membershipreport.

In operations 609 and 610, when the service flow information about thecorresponding multicast session information does not exist, themulticast controller 406 generates the service flow information andrecords the service flow information in the multicast service flowinformation tables 203 and 403.

In operation 611, when the membership request is different from thereport message based on the determining in operation 605, the multicastcontroller 406 determines whether the membership request corresponds toa leave message of requesting membership leave. When the membershiprequest corresponds to the leave message, the multicast controller 406determines whether the corresponding session information exists in themulticast session lookup tables 202 and 402.

When the corresponding session information is retrieved in operation611, the multicast controller 406 searches for the service flowinformation corresponding to the session information in operation 613and deletes or maintains the service flow based on a service flowprocessing algorithm or changes information in operation 614.

In operation 612, the multicast controller 406 does not perform aparticular operation with respect to a message excluding a membershipjoining request and a membership leave request.

An algorithm requested for generating or deleting the multicast serviceflow with respect to a multicast session in the multicast controller 406may compose an optimized algorithm based on a logical topology of a MACdomain in a cable network, a DOCSIS version incompatibility of CMs, andthe like. However, a configuration of the algorithm requested forgenerating or deleting the multicast service flow is excluded from therange of the present invention and any well-known technology may beused.

The method of processing the multicast service flow according to theabove-described exemplary embodiments may be recorded incomputer-readable media including program instructions to implementvarious operations embodied by a computer. The media may also include,alone or in combination with the program instructions, data files, datastructures, and the like. The media and program instructions may bethose specially designed and constructed for the purposes of the presentinvention, or they may be of the kind well-known and available to thosehaving skill in the computer software arts. Examples ofcomputer-readable media include magnetic media such as hard disks,floppy disks, and magnetic tape; optical media such as CD ROM disks andDVD; magneto-optical media such as optical disks; and hardware devicesthat are specially configured to store and perform program instructions,such as read-only memory (ROM), random access memory (RAM), flashmemory, and the like. Examples of program instructions include bothmachine code, such as produced by a compiler, and files containinghigher level code that may be executed by the computer using aninterpreter. The described hardware devices may be configured to act asone or more software modules in order to perform the operations of theabove-described embodiments of the present invention.

According to the present invention, a Cable Modem Termination System(CMTS) may classify a multicast session and a multicast service flowusing an efficient scheme with respect to a multicast packet coming froma network, and transmit a packet outputted by a multicast processingresult to a CM through the same downstream scheduling as a differentservice flow and a MAC header processing process in a MAC layer of theCMTS without separate additional processing.

Although a few exemplary embodiments of the present invention have beenshown and described, the present invention is not limited to thedescribed exemplary embodiments. Instead, it would be appreciated bythose skilled in the art that changes may be made to these exemplaryembodiments without departing from the principles and spirit of theinvention, the scope of which is defined by the claims and theirequivalents.

1. A method of processing a multicast service flow in a Cable ModemTermination System (CMTS), the method comprising: classifying aninputted multicast packet by a session, wherein the classified multicastpacket has a first service flow, which is based on the inputtedmulticast packet, and wherein the classified multicast packet has afirst downstream-schedule, which is based on the first service flow ofthe inputted multicast packet; searching for an address of a serviceflow information table from a multicast lookup table including serviceflow address information corresponding to the classified multicastsession; extracting internal header information including downstreamservice identifier information from the service flow information table;composing an internal header including multicast service flowinformation allocated to the classified session; and outputting aninternal multicast packet including the internal header, wherein theinternal multicast packet is outputted having the first downstreamschedule, and wherein the internal multicast packet is outputted havinga second service flow, which the internal multicast packet is outputtedwith a same scheme used for the downstream scheduling as if the firstservice flow was used, and wherein the first service flow is differentthan the second service flow.
 2. The method of claim 1, wherein themulticast lookup table is composed to search for the address of theservice flow information table using a receiving group address of theinputted multicast packet and a transmission address as a searchcharacter string.
 3. The method of claim 1, wherein the service flowinformation table includes at least one of information concerningwhether a channel bonding service of the inputted multicast packet isprovided, transmission priority information, a downstream channel list,a downstream service flow identifier, and a subsequent link address of aservice flow connected with a linked list.
 4. The method of claim 1,wherein the composing comprises: copying the inputted multicast packetthe same number of times as a number of service flows when at least onemulticast service flow allocated to the classified session exists; andcomposing a downstream service identifier with respect to acorresponding service flow and service flow information corresponding tothe downstream service identifier as the internal header in the copiedmulticast packet.
 5. The method of claim 1, further comprising:generating a multicast Media Access Control (MAC) packet based oninternal header information of the internal multicast packet, andtransmitting the MAC packet to a downstream physical layer.
 6. Themethod of claim 5, wherein the multicast MAC packet isdownstream-scheduled by the same scheme of the inputted multicast packetfor the first service flow while having the second service flow.
 7. Amethod of processing a multicast service flow in a CMTS, the methodcomprising: verifying whether an inputted downstream data packetcorresponds to a multicast packet, using a destination address of theinputted downstream data packet, wherein the classified multicast packethas a first service flow, which is based on the inputted multicastpacket, and wherein the classified multicast packet has a firstdownstream-schedule, which is based on the first service flow of theinputted multicast packet; searching for the multicast session lookuptables and verifying whether multicast session information exists whenthe inputted downstream data packet corresponds to the multicast packet;acquiring the start address of the multicast service flow informationwhen the corresponding session information exists in the multicastsession lookup tables; searching for service flow information using thestart address of the acquired service flow information; composing aninternal header including multicast service flow information allocatedto a session when the multicast session information about the inputteddownstream data packet exists; and outputting the multicast packetincluding the composed internal header, wherein the internal multicastpacket is outputted having the first downstream schedule, and whereinthe internal multicast packet is outputted having a second service flow,which the internal multicast packet is outputted with a same scheme usedfor the downstream scheduling as if the first service flow was used, andwherein the first service flow is different than the second serviceflow.
 8. The method of claim 7, wherein, when the multicast sessioninformation about the inputted downstream data packet does not exist,the internal header including information denoting a broadcast serviceflow is composed.
 9. The method of claim 7, wherein the internal headerincludes at least one of information concerning whether a channelbonding service of the multicast packet is provided, transmissionpriority information, a downstream channel list, a downstream serviceflow identifier, and a subsequent link address of a service flowconnected with a linked list.
 10. A method of processing a multicastservice flow in a CMTS, the method comprising: receiving a multicastmembership request message and generating session information;determining whether the generated session information exists in a lookuptable when the multicast membership request message corresponds to amessage of requesting group joining; searching to verify whether serviceflow information corresponding to the session information exists whenthe session information exists in the lookup table; and generating andstoring the service flow information when the service flow informationcorresponding to the session information does not exist, and wherein,when the multicast membership request message corresponds to a scheme ofidentifying a transmission area address, the receiving and generating ofthe session information adds a receiving group address and atransmission address and generates the session information, and when themulticast membership request message is different from the scheme ofidentifying the transmission area address, the receiving and generatingof the session information processes masking of the transmission addressin the receiving group address and generates the session information.11. The method of claim 10, wherein, when the multicast membershiprequest message corresponds to a message of requesting group leaving,the service flow information corresponding to the session information isdeleted or changed.
 12. An apparatus for processing a multicast serviceflow in a CMTS, the apparatus comprising: a multicast packet processorto classify an inputted multicast packet by a session, to search for anaddress of a service flow information table from a multicast lookuptable including service flow address information corresponding to theclassified multicast session, to extract internal header informationincluding downstream service identifier information from the serviceflow information table and compose an internal header, to add theinternal header to the multicast packet, the internal header includingmulticast service flow information allocated to the classified session,and to output the multicast packet, wherein the classified multicastpacket has a first service flow, which is based on the inputtedmulticast packet, and wherein the classified multicast packet has afirst downstream-schedule, which is based on the first service flow ofthe inputted multicast packet; and a header processor to compose amulticast MAC packet based on the internal header, to perform downstreamscheduling of the multicast packet using the same scheme as a generalservice flow, and to transmit the MAC packet to a downstream physicallayer, and wherein the internal multicast packet is outputted having thefirst downstream schedule, and wherein the internal multicast packet isoutputted having a second service flow, which the internal multicastpacket is outputted with a same scheme used for the downstreamscheduling as if the first service flow was used, and wherein the firstservice flow is different than the second service flow.
 13. Theapparatus of claim 12, wherein the multicast packet processor includes amulticast lookup table to be composed to search for an address of aservice flow information table using a receiving group address of theinputted multicast packet and a transmission address as a searchcharacter string.
 14. The apparatus of claim 13, wherein the serviceflow information table includes at least one of information concerningwhether a channel bonding service of the multicast packet is provided,transmission priority information, a downstream channel list, adownstream service flow identifier, and a subsequent link address of aservice flow connected with a linked list.
 15. The apparatus of claim12, wherein the multicast packet processor includes a multicastcontroller to receive a multicast membership request message, togenerate session information, and to generate or add the multicastservice flow information corresponding to the session information.